// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// +build haxe

package math

const (
	uvnan    = 0x7FF8000000000001
	uvinf    = 0x7FF0000000000000
	uvneginf = 0xFFF0000000000000
	mask     = 0x7FF
	shift    = 64 - 11 - 1
	bias     = 1023
)

// making these is expensive on most platforms, so only do it once
var f64uvnan = Float64frombits(uvnan)
var f64uvinf = Float64frombits(uvinf)
var f64uvneginf = Float64frombits(uvneginf)

// Inf returns positive infinity if sign >= 0, negative infinity if sign < 0.
func Inf(sign int) float64 {
	//var v uint64
	if sign >= 0 {
		//v = uvinf
		//return hx.GetFloat("", "Math.POSITIVE_INFINITY")
		return f64uvinf
	} else {
		//v = uvneginf
		//return hx.GetFloat("", "Math.NEGATIVE_INFINITY")
		return f64uvneginf
	}
	//return Float64frombits(v)
}

// NaN returns an IEEE 754 ``not-a-number'' value.
func NaN() float64 {
	return f64uvnan
	//return Float64frombits(uvnan)
	//return hx.GetFloat("", "Math.NaN")
}

// IsNaN reports whether f is an IEEE 754 ``not-a-number'' value.
func IsNaN(f float64) (is bool) {
	// IEEE 754 says that only NaNs satisfy f != f.
	// To avoid the floating-point hardware, could use:
	//	x := Float64bits(f);
	//	return uint32(x>>shift)&mask == mask && x != uvinf && x != uvneginf

	return f != f

	//return hx.CallBool("", "Math.isNaN", 1, f) // TODO simple comparison may be faster, but this allows for platform specifics
}

// IsInf reports whether f is an infinity, according to sign.
// If sign > 0, IsInf reports whether f is positive infinity.
// If sign < 0, IsInf reports whether f is negative infinity.
// If sign == 0, IsInf reports whether f is either infinity.
func IsInf(f float64, sign int) bool {
	// Test for infinity by comparing against maximum float.
	// To avoid the floating-point hardware, could use:
	//	x := Float64bits(f);
	//	return sign >= 0 && x == uvinf || sign <= 0 && x == uvneginf;

	return sign >= 0 && f > MaxFloat64 || sign <= 0 && f < -MaxFloat64

	// Having trouble encoding MaxFloat64 reliably in Haxe, so rewritten below
	/*
		if hx.CallBool("", "Math.isFinite", 1, f) {
			return false
		}
		if sign == 0 {
			return true
		}
		if sign > 0 {
			return f > 0
		}
		return f < 0
	*/
}

// normalize returns a normal number y and exponent exp
// satisfying x == y × 2**exp. It assumes x is finite and non-zero.
func normalize(x float64) (y float64, exp int) {
	const SmallestNormal = 2.2250738585072014e-308 // 2**-1022
	if Abs(x) < SmallestNormal {
		return x * (1 << 52), -52
	}
	return x, 0
}
